Stabilization of 1,1,1-trichloroethane



United States Patent 4 Int. Cl. C07c 17/42, 19/02 U.S. Cl. 260-6525 1Claim I ABSTRACT OF THE DISCLOSURE 1,1,l-trichloroethane is stabilizedwith a mixture comprising acetonitrile dioxane and tert. butanol.

This is a continuation of Ser. No. 316,772 filed Oct. 16, 1963, nowabandoned.

The present invention relates to' new and valuable 1,1,1-trichloroethanestabilizer combinations consisting of an organic compound containing atleast one nitrile group and at least one compound of the groupconsisting of amines, 1,4-dioxane, nitromethane and alcohols, and theinvention also includes 1,1,1-trichloroethane incorporating saidcombinations, said 1,1,1-trichloroethane exhibiting improved stability.More particularly the invention is concerned with the problem ofminimizing the marked tendency of 1,1,l-trichloroethane to undergodecomposition and relates to a process for minimizing this tendency.

It is well known that halogen hydrocarbons such as vinyl chloride,vinylidene chloride, trichloroethane, trichloroethylene,perchloroethylene, and other aliphatic chlorinated hydrocarbons veryeasily undergo decomposition. This decomposition generally takes placewith the simultaneous formation of acids and is caused, among otherthings, by the presence of light, air, or traces of Water. It isfurthermore known that the splitting otf of acid is greatly promoted bythe presence of certain metals. Thus, for example, the decompositionreaction is catalyzed by iron, aluminum, magnesium, and the alloys ofsuch metals.

The decomposition reaction can be so violent in the case of some ofthese compounds, that the further use and processing of these halogenhydrocarbons in metal vessels is possible only with the greatest ofdifliculty if at all. As noted above, light serves to promote thedecomposition further complicating further use and processing of thehalogen hydrocarbons.

This defect is especially marked in the case of 1,1,1- trichloroethane,1,1,1-trichloroethane being more inclined to split oif hydrochloric acidand then blacken than any of the above-named chlorinated hydrocarbons.The decomposition reaction can progress to the complete resinifica-tionof the material and accordingly the usefulness of 1,1,1-trichloroethaneper se is severely limited. For industrial use, 1,1,1-trichloroethane isemployed only together with an added stabilizer.

The stabilization of 1,1,1-trichloroethane has heretofore been effectedusing for the stabilization dialkylsulfoxides, dialkylsulfites,dialkylsulfides, 1,4-dioxanes, epoxides, monoketones,trialkylsilylethers, tetralkyl compounds of tin and lead, nitroalkanes,sec. or tert. alcohols, nitriles, acetylene alcohols, oxazirines,thiazirines, oxaphosphorines, and thiaphosphorines. These knownstabilizing agents must usually be used in large quantities in orderthat there results an adequate stabilizing effect,

3,445,532 Patented May 20, 1969 ice so that the l,l,1-trichloroethanethus stabilized takes on the character of a mixture of solvents. Thestabilizer- 1,1,1-trichloroethane mixtures so characterized are suitableonly for a limited field of application. Furthermore the use of dioxaneand a number of the other conventionally employed stabilizing compoundsis furthermore undesirable from the standpoint of useful applicationsbecause of their toxicity. Certain of the conventionally usedstabilizers set out above have also proved undesirable due to the colorwhich they impart to the 1,1,1-trichloroethane while others are entirelyunsuitable due to their great chemical reactivity with the agents to betreated whereby they are used up in the reaction and the stabilizingelfect produced gradually lost, decomposition thereupon setting in.Still another group of the known stabilizers is characterized by thegroups great sensitivity to hydrolysis in oxygen and therefore thisgroup finds only limited application.

It is one of the objects of the present invention to provide new andvaluable compositions which have proved of value in the stabilization of1,1,l-trichloroethane.

Another object of the present invention is to provide a simple andelfective procedure of stabilizing 1,1,1-trichloroethane.

A further object of the present invention is to provide stabilized1,1,1-trichloroethane containing such stabilizing compositions andespecially 1,1,l-trichloroethane stabilized by a mixture of an organiccompound containing at least one nitrile group and at least one compoundof the group consisting of amines, 1,4-dioxane, nitromethane, andalcohols.

Other objects of the present invention and advantageous features thereofwill become apparent as the invention proceeds.

It has been found that the stabilization of 1,1,l-trichloroethane isobtained by incorporation in the 1,1,1-trichloroethane of a mixture ofan organic compound having at least one nitrile group with at least onemember of the group consisting of amines, 1,4-dioxane, nitromethane, oralcohols. The stabilizing effect is achieved by the addition to the1,1,1-trichloroethane of a mixture of an organic compound having atleast one nitrile group and an amine, 1,4-dioxane, nitromethane, or analcohol; however, it has been further found that additional improvementsin the stabilization effect can be achieved by using as stabilizer acombination of the organic nitrile with two stabilizing agents.

Instances of nitriles suitable as components for the stabilizing mixtureinclude for example: acetoni-trile, propionitrile, acrylonitrile,fi-methoxypropionitrile, dimethylaminoacetonitrile,methylaminopropionitrile, methyleneaminoacetonitrile,dimethylaminopropionitrile, diethylaminoacetonitrile,methylethylaminoacetonitrile, malodinitrile, and thiodipropionitrile, aswell as the monoand polycyanethylated products of acetone,methylethylketone and acetic acid ester.

The amines which have proven especially elfective for use in thestabilizing combinations of the invention are those having more than oneamino group in the molecule. While the monoamines have proved to besatisfactory, the effectiveness of the monoamines in the stabilizingmixtures is far exceeded by diamines, as for instance by ethylenediamineand by other polyamines. Examples of amines suitable for use in thestabilizing of l,1,1-trichlo roethane include: triallylamine,di-n-butylamine, dimethylaniline, triethylarnine, n-butylamine,ethylenediamine, etc.

As alcohol components for the stabilizing mixture, there may be used thesaturated and unsaturated primary, secondary, and tertiary alcohols,preferably having up to 5 carbon atoms per OH group as for examplemethanol, ethanol, n-propanol, n-butanol, tert. butanol, allyl alcohol,

and propargyl alcohol. However, ketone alcohols, such as for example,4-hydroxybutanone-(2) or S-hydroxy-pentanone-(3) and the products of thecondensation of C to C amines with formaldehyde or acetaldehyde can besatisfactorily combined with the nitriles to stabilize methylchloroform.

The stabilizer compositions of the present invention are employed inquantities of about 0.05 to weight percent but preferably in quantitiesof 0.2 to 1 weight percent. An addition of 0.5 weight percent ofstabilizing 10 composition produces a stabilization of methyl chloroformthat is adequate for most practical requirements.

In the preparation of the stabilizing compositions, the amounts ofnitrile, alcohol, amine, etc. are generally employed in equivalentamounts. However, it is also possible to prepare the stabilizing mixturewith more or less of the nitrile compound being present in relation tothe other components, both types of components are, however, required tobe present in order to obtain the desired degree of stabilization.

The method of the invention for stabilizing 1,1,1-trichloroethane isespecially advantageous in that the abovedescribed stabilizercompositions are considerably more effective than any one of the singlecomponents by itself in comparable concentration, as a result of whichit is for a specific purpose can be determined, for example, by

simply boiling a specific amount of 1,1,l-trichloroethane with identicalpercentages of combinations to be evaluated in the presence of aspecific amount of a metal powder, granules or chips.

The stabilizer compositions of the present invention can be added in thevarious stages of the manufacturing process'of 1,1,l-trichloroethane. Incertain instances the presence of the stabilizing compounds may beespecially desirable in the gaseous phase, as for example in thedistillation thereof.

The following examples serve to illustrate the present inventionwithout, however, limiting the same thereto.

In the following table, there are given the efiect of a number of knownstabilizers when used each by themselves, and a number of stabilizercombinations in accordance with the invention in the stabilization of1,1,1-trichloroethane. In each case the stated amount of stabilizer orstabilizer combination and 5 grams of aluminum turnings or 5 grams ofaluminum granules wasadded to grams of 1,1,1-trichloroethane and theresulting mixture then heated under reflux until the chlorohydrocarbonblackened or until HCl was split off. The time that elapsed up to thediscoloration point or the evolution of I-ICl can be taken as a measureof the effectiveness of the tested substance or combination ofsubstances as stabilizer for 1,1,1-trichloroethane.

The examples in the table have been divided into three sections:

(I) Example in which no stabilizer is used.

(II) Examples employing for the stabilization of 1,1,1- trichloroethanethe following known stabilizers:

(a) Amines (b) 1,4-dioxane (c) Nitromethane (d) Alcohols (e) Nitriles.

(III) Examples employing for the stabilization of 1,1,1-trichloroethanethe stabilizer combinations in accordance with the invention.

Example Time to r splitting 05 Amount of H01 or added, wt. to blackening(min.

Stabilizer percent I II-a III .... Ethylenediamine.-

Nitromethane- Tert. butanol Tert.butanol None Triallylamine lDi-n-butylamine 1,4-dioxane N itromethane Ethyl alcohol Allyl ale0holPropargyl alcohol 13 Tert. butanol L... 14 Acryionitrile 15 Acetonitrilel 16 fl-Methoxypropionitrile 17 Methyleneaminacetonitrile 18Dicyanethylated methylethylketone 19 Dieyanethylated acetic acid ester20 Acetonitn'le 21 Acetonitrile 1,4-riioxane 22 B-Methoxypropionitrile23 Acetonitrile 1,4-rii0xarm 24 Acetonitrile L-.-

25 Acetonitrile 26 Aeetonitrile 2 Nitrom eth arm Tert, bntnnnl 27Acetonitrile 2 D inxan a 28 Acetonitrile lA-dioxane 29 AcetonitrileNitromethano 1,4-dioxane 30 Aeetonitrile oooooooooooooopppoo Nitrnmethane Ihe stabilization example was conducted in the presence of 5grams of aluminum urn gs.

T lile stabilization example was conducted in the presence of 5 grams ofaluminum gran 3 Hours.

5 What is claimed is as follows: 1. A stabilized 1,1,1-trichlor0ethanewhich comprises 1,1,1-trich10roethane and 0.05 to 10 weight percent of amixture containing acetonitrile, tert. butanol and dioxane.

References Cited UNITED STATES PATENTS 3,008,999 11/1961 Kaudcr 260652.5

6 3,192,273 6/1965 Bissinger 260-6525 3,265,747 8/1966 Cormany et a1.260-6525 3,251,891 5/1966 Cormany et a1. 260 652.5

LEON ZITVER, Primary Examiner. MATTHEW M. JACOB, Assistant Examiner.

U.S. Cl. X.R. 251--153, 171

